Much of the hail that falls on Europe occurs in summer though scientists believe it is caused by cold temperatures. Some meteorologists believe hail is formed when a current of hot air rises to about 1,000 to 2,000 metres and collides with a cold air current that is descending. The sudden lowering of the temperature in the warm air current freezes the moist air it contains into the little pellets of ice that form hail. This process may be repeated several times, the hailstone gathering more and more coatings of ice, until it becomes heavy and falls.
Other meteorologists think that hail is produced by electrical processes.
Whatever the cause hail is a constant threat to farmers who for centuries have sought ways of defending their fields from it. Hailstorms do not usually affect large areas, but they can be so concentrated and intense that they destroy an entire year’s crop wherever they strike. Vineyards are frequently affected in this way.
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